Undergarment

Undergarments or underwear are clothes worn under other clothes, often next to the skin. They keep outer garments from being soiled by perspiration, urine, semen, feces, and other discharges; shape the body; and provide support for parts of it. In cold weather, long underwear sometimes is worn to provide additional warmth. Some undergarments are intended for erotic effect. Special types of undergarments have religious significance. Some items of clothing are designed as underwear, while others, such as T-shirts and certain types of shorts, are appropriate both as undergarments and as outer clothing. If made of suitable material, some undergarments can serve as nightwear or swimsuits.
Undergarments commonly worn by women today include brassieres and panties (also known as knickers), while men often wear briefs, boxer shorts, and boxer briefs. Items commonly worn by both sexes include T-shirts, sleeveless shirts (also called singlets), bikini underwear, thongs, and G-strings.

Terminology
There are several other terms for undergarments. Underclothes, underclothing and underwear are formal terms, while undergarments may be more casually called, in Australia, Reg Grundys (rhyming slang for undies) and Reginalds, and, in the United Kingdom, smalls (from the earlier smallclothes).
Women's undergarments collectively are called lingerie. They also are called intimate clothing and intimates.
An undershirt is a piece of underwear covering the torso, while underpants (often pants in the United Kingdom), drawers, and shorts cover the genitals and often the buttocks. Terms for specific undergarments are in the table below.

---Frankie